Starting and operating apparatus for electric discharge lamps



Nov. 1, 1955 J. CATES ET AL STARTING AND OPERATING APPARATUS FOR ELECTRIC DISCHARGE LAMPS Filed March 25, 1952 m y e I 3 m o mmw o mC. m L e S u mum .m 1. m/W y b w u United States Patent STARTING AND OPERATING APPARATUS FOR ELECTRIC DISCHARGE LAMPS Julius Cates and Henry G. Jenkins, Wembley, England, asslgnors to General Electric Company, a corporation of New York Application March 25, 1952, Serial N 0. 278,458

4 Claims. (Cl. 31596) This invention relates to apparatus for operating from an alternating supply low pressure electric discharge lamps of the kind having heatable electrodes, and relates especially to apparatus for reliably starting and op erating the well known low pressure mercury vapor tubular fluorescent lamps of this kind from public supply mains.

According to the invention an apparatus for operating from an alternating supply a low pressure electric discharge lamp of the kind having heatable electrodes comprising input terminals for connection to the supply, an electrode heating transformer having its primary winding connected directly between said input terminals and having a pair of secondary windings connectable each to one of the lamp electrodes for the supply of heating current thereto, each secondary winding being connected to a different input terminal for applying at least the supply voltage between said electrodes, at least one of said connections including an inductive impedance forming part or the whole of the ballast impedance for the lamp, and a starting switch connected between said secondary windings and arranged so as in operation first to close or be closed for connecting said inductive impedance across the input terminals and thereafter to be opened and break the current flow through said impedance so as to generate a high voltage pulse for starting the lamp discharge.

The secondary windings may be connected in voltage aiding or opposition relative to the primary winding; the former will assist starting whereas the latter will reduce the load on the transformer and the choice between them will depend on which of these factors is the more important in any particular case.

The starting switch may be of any suitable kind, either manually or automatically operated. If the latter, it may be operated by any suitable means. For example, it may be of the glow discharge kind or it may be of the resistance heated kind. In the former case, the contacts of the switch are normally open and are heated by the glow discharge set up by the voltage existing before starting of the lamp so as to close, thereby shorting out the glow discharge, and thereafter opening on cooling, the voltage existing after starting of the lamp being insufiicient to cause the glow discharge to restrike. In some cases the lamp may start under the influence of the heating of the electrodes produced by the electrode heating transformer and the applied supply voltage before the glow switch has time to operate, especially if, as is preferred, the lamp is provided with an earthed starting stripe, but the presence of the starting switch ensures reliable starting at low ambient temperatures or low supply voltages, or both, when the switch may be brought into action.

In the case of a resistance heated, or electromagnetically actuated, starting switch, the contacts are normally closed and the switch actuator is arranged in series with the inductive ballast impedance so that it is always first energized before starting of the lamp by the flow of current through that impedance to open the switch, and

Patented Nov. 1, 1955 thereafter is energized by the lamp discharge current to hold the switch open during operation of the lamp.

It will be appreciated that apparatus in accordance with invention may be adapted for the operation of a plurality of lamps either in series or in parallel or in series parallel. When lamps are in series, one of the said pair of secondary windings is connected to the first electrode of the lamp at one end of the series of lamps and the other of the said pair of secondary windings is connected to the last electrode of the lamp at the other end of the series, the connected-together intermediate lamp electrodes being connected for the supply of heating current to one or more further secondary windings on the electrode heating transformer. In such an arrangement each lamp may be arranged to be shunted by a starting switch or a single switch may shunt all the lamps.

An object of this invention is to provide a form of apparatus which will ensure reliable starting of a lamp or lamps operated by it even in conditions of low ambient temperature, for example at 20 C., or at considerable reductions in the supply voltage from its nominal value, or both.

The invention will be better understood from the following description taken in connection with the accompanying drawing and the scope will be pointed out in the appended claims.

In the drawing, Fig. l is a diagrammatic illustration of an embodiment of the invention in which the inductive ballast impedance for the discharge lamp is also a transformer secondary winding and in which the starting switch is of the glow discharge type and Fig. 2 illustrates a modification in which two lamps are operated in series with an ordinary inductive ballast winding and in which the starting switches are of the resistance heated kind.

Referring now to the drawing and more particularly to Fig. 1, the apparatus comprises essentially a transformer having a primary winding 1 connected between a pair of input terminals 2 and a pair of secondary windings 3 and 4 for energizing respectively separate heatable electrodes 5 and 6 of an electric discharge lamp 7 which may be of the low pressure mercury vapor tubular fluorescent type. The transformer is also provided with main output terminals 8 connected respectively to the secondary windings 3 and 4. Serially connected between one input terminal and one output terminal is an inductive ballast winding 9 which is shown by way of example as being inductively related to the primary winding 1 so that it has a voltage induced in it for stepping up by auto transformer action the voltage impressed between input terminals 2 on the primary winding 1. The requisite ballasting reactance is obtained by the degree of coupling or flux leakage between the primary winding 1 and the ballasting winding 9 which coupling may be relatively loose or relaxed as is well known in the art.

Also connected between the output terminals 8, and therefore also connected between the secondary windings 3 and 4 is a starter switch 10 and radio interference suppressing capacitor 11. The switch 10 is of the socalled glow discharge type in which the contacts are normally open but are closed under the influence of heat developed by an electric discharge between them.

The operation of Fig. 1 is as follows: When the input terminals 2 are connected to any suitable source of supply voltage such as an ordinary alternating current house-lighting circuit, the voltage induced by the primary winding 1 in the secondary windings 3 and 4 causes heating current to flow through the electrodes 5 and 6 of the lamp 7. At the same time, the voltage of the primary winding 1 plus any voltage induced by that winding in the ballast winding 9 is impressed between the electrodes 5 and 6 and is also impressed between the open contacts of the starter switch 10. As is well known, the latter is so constructed that under these voltage conditions, a glow discharge occurs between its contacts thus heating the switch and causing the contacts to close. As soon as the contacts of the starter switch close, the glow discharge ceases and the switch cools and reopens its contacts thus producing an inductive kick in the winding 9 which coupled with the ordinary steady state voltages induced in the windings 1 and 9 is sufficient to initiate an are discharge in the lamp 7 with its electrodes 5 and 6 heated to electron-emitting temperatures by the secondary windings 3 and 4. After the lamp 7 has started, its voltage drop will be insufiicient to maintain a glow discharge in the starter switch 10 and consequently its contacts will remain open.

The arrangement shown in Fig. 2 comprises an electrode heating transformer whose primary winding 12 is connected directly between the input terminals 13 and 13'. The transformer has three secondary windings 14, 15, and 16 of which 14 is connected across one electrode 17 of a first low pressure electric discharge lamp 18, and is connected across one electrode 19 of a second similar lamp 20. Across the third secondary winding 16 are connected in series the remaining two electrodes 21 and 22 of the lamps 18 and 20, the lamps being thereby connected in series.

One side of the secondary winding 14 is connected to the input terminal 13 through the heater winding 23 of a first thermal switch and, in series, a ballast inductance 24 for the two lamps. The contacts 25 of the thermal switch are connected between the electrodes 17 and 21, between which is also connected an interference suppression condenser 26.

One side of the secondary winding 15 is connected to the input terminal 13' through the heater winding 27 of a second thermal switch whose contacts 28 are connected between the electrodes 19 and 22, between which is also connected an interference suppression condenser 29.

In the operation of this embodiment, on connection of the input terminals to a suitable source of supply (13' being preferably connected to the neutral or normally grounded side of the supply), heating current is supplied to the four electrodes of the two lamps from the transformer secondary windings. At the same time current flows through the closed circuit formed by the inductance 24, heater 23, closed contacts 25, secondary 1 6, closed contacts 28 and heater 27 and the heaters 23 and 27 heat up until one of the contacts 25 and 28 opens, breaking the flow of current through the inductance 24. An inductive kick is then generated and starts the discharge in the corresponding lamp. Current continues to flow through the other heater and this opens the other of the contacts 25 or 28, again breaking the current through the inductance 24 and generating a further voltage pulse which leads to the starting of the second lamp and the restarting of the first. Thereafter the contacts 25 and 28 are held open by the flow of the lamp discharge current through the heaters 23 and 27.

The initial heating of the electrodes by the electrode heating transformer combined with the high voltage starting pulses produced by the action of the thermal switches ensures reliable starting even at low ambient temperatures and low supply voltages.

While I have shown particular embodiments of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for starting and operating a cathode type electric discharge lamp comprising, in combination, a transformer having a glow 'discharge starter switch, said transformer having a main primary winding and three secondary windings connected in auto transformer relationship with respect to said primary winding, one of said secondary windings being a ballasting winding and the other two of said secondary windings being cathode heater current supplying windings, said primary winding and said ballast secondary winding being serially connected between said remaining two'secondary windings, said glowdischarge starter switch being connected in parallel circuit relation with said primary winding and ballast secondary Winding.

2. Apparatus for low temperature starting and operating and electric discharge lamp of the fluorescent type comprising a step-up auto transformer having a pair of additional secondary windings connected respectively to the terminals of said auto transformer windings, said additional secondary windings being adapted to supply heating current for different electrodes of an electric discharge lamp of the fluorescent type, said auto transformer windings being adapted to supply starting and operating voltage between the electrodes of said lamp and to provide a ballasting action for the lamp current, and a thermal starter switch connected between said additional secondary windings.

3. Apparatus for low temperature starting and operating, a pair of heatable electric discharge lamps in series comprising, in combination, a transformer having a primary winding and three secondary windings, one of said secondary windings being connected to supply heating current to electrodes of different ones of said lamps, the other two secondary windings being adapted to supply heating current to the remaining two electrodes of said lamps, a pair of resistance-heated thermal switches having their contacts connected respectively between the first secondary winding and the remaining two secondary windings, means including a resistance heater for one of said switches for connecting one end of the primary winding to one of said remaining secondary windings, means including a ballast winding and a resistance heater of the other thermal switch for connecting the other end of the primary winding to the other one of said remaining additional secondary windings, and separate radio interference suppression capacitors connected respectively between the first secondary winding and the remaining two secondary windings.

4. Apparatus for starting and operating in series a pair of heatable cathode electric discharge lamps comprising, in combination, a transformer having a primary winding and three secondary windings, one of said secondary windings being for supplying heating current to two electrodes of different electric discharge lamps, the remaining secondary windings being for supplying heating current to the remaining electrodes of said lamps, a ballast winding connected in circuit between one of said remaining secondary windings and one side of said primary winding, the other of said remaining secondary windings being connected in circuit with the other side of said primary winding, and separate starter switches connected respectively between said one secondary winding and said remaining secondary windings.

References Cited in the file of this patent UNITED STATES PATENTS 2,294,623 LeBrun Sept. 1, 1942 2,455,791 Masciarelli Dec. 7, 1948 2,507,101 Hall May 9, 1950 2,518,767 Freeman Aug. 15, 1950 2,518,874 Feinberg Aug. 15, 1950 

